In communications, especially base-stations for mobile telecommunications there is a requirement to retrieve the original signal from the receiver channel. The received signal is often subject to strong distortion due to multi-path effects i.e. signal reflections caused by interference in built-up urban areas, for example. Each multi-path is often known as a finger.
Extracting data for each individual finger from the composite received signal is possible with knowledge of the associated phase delay. More specifically, the required data for each finger is a subset of the received data stream (which in turn is sub-sampled) with a different phase delay according to the different expected round trip delay of that particular multi-path between the sender and the receiver. These sub-sampled data sets need to be coherently summed by a subsequent processing phase to maximise the S/N (Signal to Noise) ratio of the received signal.
Determining knowledge of these phase delays and thereafter using these to extract the relevant information regarding each finger is a non-trivial task. Nevertheless techniques are known for performing this processing. For example, the different phase delays can be determined by an earlier matched filter step (correlation) against a known sequence in each frame—which obtains the energy peaks—which in turn correspond to the strong multi-paths. This data provides the information required in order to control the subsequent received data processing.
In order to be able to perform the various different types of processing techniques required on the received data to improve the S/N ratio, powerful computers are required. However, due to the time constraints of wishing to perform this processing in real time as the data is being received, namely on-the-fly, the S/N ratio of the processed signal is low, which turn leads to a relatively low-quality received signal.